First, educate yourself by reading about the subject. However, don't get stuck into thinking you have to know everything to begin, you don't.
Start with friends and family who are supportive. Ask them if they know people who would like to help you by coming to a gold valuation party. Take business cards, as I've explained in the article. The plus side of doing it this way, is you'll be in a supportive environment and gain confidence. No one expects you to be perfect if you're just starting out.
Another option is, to get a temporary job at a place that buys and sells. There you'll be dealing with the public but with the guidance of others. Then, when you know the business, step out on your own.